The gifts -- which include items like cupcakes from Magnolia Bakery, a stuffed animal from Gund, or a digital gift card from Starbucks -- can be sent from a user's birthday reminders or from a friend's timeline. Other gifts, plucked from more than 100 retailer partners, include fresh flowers, a bacon of the month club, and an Uber cab ride.

It's a big step for Facebook, which is feeling pressure from investors to find news ways of making money. The company's stock finished at $20.32 today, down from its opening day high earlier this year of $45. With Wall Street on its back, the social network is creating an e-commerce system within its own world, one you can bet doesn't have room for the likes of retail giants like Amazon or eBay.

Not only does this give Facebook another revenue stream, it potentially lets the social network show off some mobile chops. Adding the feature on mobile -- if it actually functions smoothly -- lets the company cash in on the growing mobile shopping market, which some say is bringing in billions.

To buy a gift using the new Facebook feature, people hit the gift button on a friend's Timeline or on any of the birthday reminders that pop up on their profile (see image above). After choosing a gift, they select a card, review, and send. Facebookers can pay right away or add payment details later, according to the social network. When a friend gets the gift, he or she will be able to preview it and enter an address for shipment. The feature even gives friends the option of exchanging the gift.

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Facebook's not revealing how much money it's making off each sale, except to say "we have a sliding scale that varies based on the product and partner." The service -- which is available on Android devices, the mobile Web, and the desktop -- is rolling out in the U.S. first. It will come to iOS devices in a few weeks, a Facebook representative said.

Other real gifting services on Facebook, like Wrapp or Boomerang, must be shaking in their boots. Here's a competing service that is seamlessly integrated into Facebook's system.